A client-side XHR request for getting data from a URL, formally known as XMLHttpRequest.
HttpRequest can be used to obtain data from HTTP and FTP protocols, and is useful for AJAX-style page updates.
The simplest way to get the contents of a text file, such as a JSON-formatted file, is with getString. For example, the following code gets the contents of a JSON file and prints its length:
var path = 'myData.json';
HttpRequest.getString(path)
.then((String fileContents) {
print(fileContents.length);
})
.catchError((Error error) {
print(error.toString());
});
Fetching data from other servers
For security reasons, browsers impose restrictions on requests made by embedded apps. With the default behavior of this class, the code making the request must be served from the same origin (domain name, port, and application layer protocol) as the requested resource. In the example above, the myData.json file must be co-located with the app that uses it. You might be able to get around this restriction by using CORS headers or JSONP.
Other resources
-
Fetch Data Dynamically, a tutorial from A Game of Darts, shows two different ways to use HttpRequest to get a JSON file.
-
Get Input from a Form, another tutorial from A Game of Darts, shows using HttpRequest with a custom server.
- Dart article on using HttpRequests
- JS XMLHttpRequest
- Using XMLHttpRequest
- Inheritance
- Object
- JSObject
- DartHtmlDomObject
- EventTarget
- HttpRequestEventTarget
- HttpRequest
- Annotations
- DomName('XMLHttpRequest')
Constants
- DONE → int
-
4 - HEADERS_RECEIVED → int
-
2 - LOADING → int
-
3 - OPENED → int
-
1 - readyStateChangeEvent → EventStreamProvider<ProgressEvent>
-
Static factory designed to expose
readystatechangeevents to event handlers that are not necessarily instances of HttpRequest.…const EventStreamProvider<ProgressEvent>('readystatechange') - UNSENT → int
-
0
Static Properties
- instanceRuntimeType → Type
-
read-only
- supportsCrossOrigin → bool
-
Checks to see if the current platform supports making cross origin requests.…
read-only - supportsLoadEndEvent → bool
-
Checks to see if the LoadEnd event is supported on the current platform.
read-only - supportsOverrideMimeType → bool
-
Checks to see if the overrideMimeType method is supported on the current platform.
read-only - supportsProgressEvent → bool
-
Checks to see if the Progress event is supported on the current platform.
read-only
Static Methods
-
getString(
String url, {bool withCredentials, void onProgress(ProgressEvent e)}) → Future<String> -
Creates a GET request for the specified
url.… -
postFormData(
String url, Map<String, String> data, {bool withCredentials, String responseType, Map<String, String> requestHeaders, void onProgress(ProgressEvent e)}) → Future<HttpRequest> -
Makes a server POST request with the specified data encoded as form data.…
-
request(
String url, {String method, bool withCredentials, String responseType, String mimeType, Map<String, String> requestHeaders, sendData, void onProgress(ProgressEvent e)}) → Future<HttpRequest> -
Creates and sends a URL request for the specified
url.… -
requestCrossOrigin(
String url, {String method, String sendData}) → Future<String> -
Makes a cross-origin request to the specified URL.…
Constructors
- HttpRequest()
-
General constructor for any type of request (GET, POST, etc).…
factory - HttpRequest.internal_()
Properties
- hashCode → int
-
read-only, inherited
- on → Events
-
This is an ease-of-use accessor for event streams which should only be used when an explicit accessor is not available.
read-only, inherited - onAbort → Stream<ProgressEvent>
-
Stream of
abortevents handled by thisHttpRequestEventTarget.read-only, inherited - onError → Stream<ProgressEvent>
-
Stream of
errorevents handled by thisHttpRequestEventTarget.read-only, inherited - onLoad → Stream<ProgressEvent>
-
Stream of
loadevents handled by thisHttpRequestEventTarget.read-only, inherited - onLoadEnd → Stream<ProgressEvent>
-
Stream of
loadendevents handled by thisHttpRequestEventTarget.read-only, inherited - onLoadStart → Stream<ProgressEvent>
-
Stream of
loadstartevents handled by thisHttpRequestEventTarget.read-only, inherited - onProgress → Stream<ProgressEvent>
-
Stream of
progressevents handled by thisHttpRequestEventTarget.read-only, inherited - onReadyStateChange → Stream<ProgressEvent>
-
Event listeners to be notified every time the
HttpRequestobject'sreadyStatechanges values.read-only - onTimeout → Stream<ProgressEvent>
-
Stream of
timeoutevents handled by thisHttpRequestEventTarget.read-only, inherited - readyState → int
-
Indicator of the current state of the request:…
read-only - response → Object
-
The data received as a reponse from the request.…
read-only - responseHeaders → Map<String, String>
-
Returns all response headers as a key-value map.…
read-only - responseText → String
-
The response in String form or empty String on failure.
read-only - responseType → String
-
Stringtelling the server the desired response format.…read / write - responseUrl → String
-
read-only
- responseXml → Document
-
The request response, or null on failure.…
read-only - runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited - status → int
-
The HTTP result code from the request (200, 404, etc). See also: HTTP Status Codes
read-only - statusText → String
-
The request response string (such as \"200 OK\"). See also: HTTP Status Codes
read-only - timeout → int
-
Length of time before a request is automatically terminated.…
read / write - upload → HttpRequestUpload
-
EventTargetthat can hold listeners to track the progress of the request. The events fired will be members ofHttpRequestUploadEvents.read-only - withCredentials → bool
-
True if cross-site requests should use credentials such as cookies or authorization headers; false otherwise.…
read / write
Operators
-
operator ==(
other) → bool -
The equality operator.…
inherited
Methods
-
abort(
) → void -
Stop the current request.…
-
addEventListener(
String type, EventListener listener(Event event), [bool useCapture]) → void -
inherited
-
dispatchEvent(
Event event) → bool -
inherited
-
getAllResponseHeaders(
) → String -
Retrieve all the response headers from a request.…
-
getResponseHeader(
String name) → String -
Return the response header named
header, or null if not found.… -
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed.…
inherited -
open(
String method, String url, {bool async, String user, String password}) → void -
Specify the desired
url, andmethodto use in making the request.… -
overrideMimeType(
String mime) → void -
Specify a particular MIME type (such as
text/xml) desired for the response.… -
removeEventListener(
String type, EventListener listener(Event event), [bool useCapture]) → void -
inherited
-
send(
[body_OR_data]) → void -
setRequestHeader(
String name, String value) → void -
Sets the value of an HTTP requst header.…
-
toString(
) → String -
Returns the result of the JavaScript objects
toStringmethod.inherited